Refastenable mechanical fastening system

ABSTRACT

The invention is a refastenable mechanical fastening system, made of free formed prongs joined to a substrate. The prongs taper and are nonperpendicularly oriented relative to the plane of the substrate. The prongs also have an azimuthal angle relative to the machine direction of the substrate. Each prong has an engaging means projecting laterally from the periphery of the prong. The free formed prongs are manufactured by the process of depositing liquid material onto a moving substrate, stretching the liquid material in a direction parallel to the plane of the substrate, severing the stretched material to form the distal end and engaging means of the prong, and imparting an azimuthal angle to the prong. The advantageous usage of the fastening system in an article of manufacture, such as a disposable absorbent garment, specifically a diaper, is also disclosed.

This is a continuation of application Ser. No. 07/979,726, filed on Nov.20, 1992 now abandoned; which is a divisional of application Ser. No.07/632,283, filed on Dec. 21, 1990 now U.S. Pat. No. 5,180,534; and is acontinuation-in-part of application Ser. No. 07/668,817, filed on Mar.7, 1991 now U.S. Pat. No. 5,230,851; which is a continuation ofapplication Ser. No. 07/305,354, filed on Jan. 31, 1989 now abandoned.

FIELD OF THE INVENTION

The present invention relates to refastenable mechanical fasteningsystems, more particularly to fastening systems having free formedprongs and the process of manufacturing such fastening systems.

BACKGROUND OF THE INVENTION

Refastenable mechanical fastening systems are well known in the art.Typically, such fastening systems involve two major components, a prongwhich is joined to a substrate and engages with a complementary secondcomponent, the receiving surface. A projection of the prong of thefastening system penetrates the receiving surface and either engages orintercepts strands or fibers of the receiving surface. The resultingmechanical interference and physical obstruction prevent removal of thefastening system from the receiving surface until the separation forcesexceed either the peel or shear strength of the fastening system.

Presently, refastenable mechanical fastening systems are made by atleast two general methods. One method requires a plurality of filaments,each of which may be formed into two prongs. Examples of fasteningsystems produced by this method are shown in U.S. Pat. No. 2,717,437,issued Sep. 13, 1955 to de Mesteral and U.S. Pat. No. 3,943,981, issuedMar. 16, 1976 to De Brabandar which teach a raised pile of loops.Related teachings are shown in U.S. Pat. No. 4,216,257, issued Aug. 5,1980 to Schams et al., U.S. Pat. No. 4,454,183, issued Jun. 12, 1984 toWollman and U.S. Pat. No. 4,463,486, issued Aug. 7, 1984 to Matsuda.These references teach heating the ends of polymeric monofilaments.Other related teachings of fastening systems produced by the firstmethod are disclosed in U.S. Pat. No. 4,307,493, issued Dec. 29, 1981 toOchiai and U.S. Pat. No. 4,330,907, issued May 25, 1982 to Ochiai.

The second general method commonly utilized to manufacture mechanicalfastening systems is to mold or extrude the systems as illustrated inU.S. Pat. No. 3,147,528, issued Sep. 8, 1964 to Erb and U.S. Pat. No.3,594,863, issued Jul. 27, 1971 to Erb. Continuous injection molding istaught in U.S. Pat. No. 3,594,865, issued Jul. 27, 1971 to Erb.

Various prong structures are illustrated in the prior art. For example,the references discussed above teach fastening systems having stems ofgenerally constant cross section. U.S. Pat. No. 3,708,833, issued Jan.9, 1973 to Ribich et al. discloses a prong which is somewhat taperedfrom the proximal end to the distal end and perpendicularly projectsfrom the substrate.

European Patent Application No. 0,276,970, filed Jan. 26, 1988, by theProcter & Gamble Company in the name of Scripps discloses a fasteningdevice having a constant cross section stem oriented at an angle betweenabout 30° and about 90° relative to the base.

The prior art does not show methods of manufacture which produce freeformed prongs. The prior art also does not show the structure of amechanical fastening system wherein the prong is nonperpendicularlyoriented relative to the substrate and has tapered sides. The prior artalso does not show methods of manufacture which produce free formedprongs oriented substantially in the cross-machine direction of thesubstrate.

It is an object of this invention to provide a free formed mechanicalfastening system produced by a method of manufacture similar to gravureprinting. It is also an object of this invention to provide a fasteningsystem having tapered prongs which do not perpendicularly project fromthe associated substrate. It is a further object of this invention toprovide a fastening system having free formed prongs which are orientedsubstantially in the cross-machine direction of the substrate.

BRIEF SUMMARY OF THE INVENTION

The invention comprises a fastening system for attaching to acomplementary receiving surface. The fastening system has a substrateand at least one free formed prong comprising a base, shank and engagingmeans. The base of the prong is joined to the substrate and the shank iscontiguous with and projects outwardly from the base. The engaging meansis joined to the shank and projects laterally beyond the periphery ofthe shank. The shank is nonperpendicularly oriented relative to theplane of the substrate. The shank has a leading edge and a trailing edgedefining a leading angle and trailing angle respectively. The leadingangle and trailing angle are substantially different from each other, sothat the sides of the shank are nonparallel. The shank also has anazimuthal angle. The azimuthal angle can be between about 1° and about180°, preferably between about 20° to about 160°, relative to the MD.

The fastening system may be made according to the process comprising thesteps of heating a thermally sensitive material sufficiently to reduceits viscosity for processing, and preferably to at least its meltingpoint. A means to deposit discrete amounts of the heated material isprovided. The substrate to which the material is to be joined istransported in a first direction relative to the means for depositingthe material. The material is deposited on the transported substrate indiscrete amounts. The discrete amounts of material are then stretched ina direction having a vector component generally parallel to the plane ofthe substrate. The stretched material is severed to form a distal endand engaging means, and an azimuthal angle between about 1° to about180°, preferably between about 20° to about 160°, is imparted to theshank.

An illustrative and suitable, but nonlimiting, use for the fasteningsystem produced by the process of the present invention is inconjunction with a disposable absorbent garment, such as a diaper. Thisexample of one usage of the present invention is more fully describedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

While the Specification concludes with claims particularly pointing outand distinctly claiming the invention, it is believed the invention willbe better understood from the following description taken in conjunctionwith the associated drawings in which like elements are described by thesame reference numeral and related elements are designated by adding oneor more prime symbols or incrementing the numeral by 100:

FIG. 1 is a perspective view of a fastening system of the presentinvention wherein the engaging means are oriented in substantially thesame direction;

FIG. 2 is a side elevational view of one prong of the fastening systemshown in FIG. 1;

FIG. 3 is a side elevational view of a second embodiment having agenerally semispherically shaped engaging means;

FIG. 4 is a side elevational schematic view of one apparatus which canbe used to produce the fastening system of the present invention;

FIG. 5 is a perspective view of a fastening system of the presentinvention wherein the engaging means are oriented in substantiallyrandom directions;

FIG. 6 is a perspective view of a disposable absorbent garment utilizingthe fastening system of the present invention, showing the topsheet andcore partially in cutaway;

FIG. 7 is a top plan view of one prong having an azimuthal angle ofabout 90°;

FIG. 8 is a front elevational view of one apparatus (only a portion ofwhich is shown) which can be used to produce the fastening system of thepresent invention having azimuthally angled prongs;

FIG. 9 is a top plan view of a second apparatus which can be used toproduce the fastening system of the present invention having azimuthallyangled prongs.

DETAILED DESCRIPTION OF THE INVENTION

The fastening system 20 of the present invention comprises at least oneprong 22, and preferably an array of prongs 22, joined to a substrate 24in a predetermined pattern as shown in FIG. 1. The prongs 22 have a base26, shank 28 and engaging means 30. The bases 26 of the prongs 22contact and adhere to the substrate 24, and support the proximal ends ofthe shanks 28. The shanks 28 project outwardly from the substrate 24 andbases 26. The shanks 28 terminate at a distal end which is joined to anengaging means 30. The engaging means 30 radially project laterally fromthe shanks 28 in one or more directions and may resemble a hook-shapedtine. As used herein, the term "lateral" means having a vector componentgenerally parallel to the plane of the substrate 24 at the principalprong 22 under consideration. The projection of an engaging means 30from the shank 28 periphery in a lateral direction allows the engagingmeans 30 to be secured to a complementary receiving surface (not shown).The engaging means 30 is joined to, and preferably contiguous with, thedistal end of the prong 22. It will be apparent the engaging means 30may be joined to the prong 22 at a position between the base 26 and thedistal end of the shank 28.

The array of prongs 22 may be produced by any suitable method, includingmethods which yield a free formed prong 22 as described and claimedhereinbelow. As used herein, the term "free formed" means a structurewhich is not removed from a mold cavity or extrusion die in solid formor with a defined shape. The prongs 22 are deposited onto anoncontiguous substrate 24 in a molten, preferably liquid state andsolidify, by cooling until rigid and preferably freezing, into thedesired structure and shape as described hereinafter.

The free formed array of prongs 22 is preferably produced by amanufacturing process which is similar to that process commonly known asgravure printing. Using this process, a substrate 24 having opposedfaces is passed between the nip 70 of two generally cylindrical rolls, aprint roll 72 and a backing roll 74, as illustrated at FIG. 4. The rolls72 and 74 have generally parallel centerlines and are maintained incontacting relationship with the substrate 24 as it passes through thenip 70. One of the rolls, referred to as the print roll 72, has an arrayof blind, closed-end cavities, referred to as cells 76, corresponding tothe desired pattern of prongs 22 to be deposited on the substrate 24.The second roll, referred to as the backing roll 74, provides thereaction against the print roll 72 to position the substrate 24 againstthe print roll 72 as the substrate 24 passes through the nip 70. Liquid,thermally sensitive material, preferably thermoplastic material, fromwhich the prongs 22 are to be formed is supplied from a heated source,such as a trough 80. The thermally sensitive material is introduced intothe cells 76 as the print roll 72 is rotated about its centerline. Thecells 76 containing the thermally sensitive material transport it untilcontact with the substrate 24 is made and deposit this material onto thesubstrate 24 in the desired pattern.

As relative displacement between the substrate 24 and rolls 72 and 74continues, the prongs 22 are stretched with a lateral component,generally parallel to the plane of the substrate 24, forming the shank28 and the engaging means 30. Finally, the moil of the prong 22 issevered from the engaging means 30 by a severing means 78. Due to theviscoelastic properties of the thermoplastic, the prong 22 contracts. Itis also believed that the prong 22 retracts under the influences ofgravity and shrinkage which occur during cooling. The prong 22 thencools, and preferably freezes, into a solid structure having theengaging means 30 contiguous with the shank 28.

The fastening system 20 is secured to a complementary receiving surface.As used herein, the term "receiving surface" to which the engaging means30 of the fastening system 20 are secured refers to any plane or surfacehaving an exposed face with tightly spaced openings complementary to theengaging means 30 and defined by one or more strands or fibers or,alternatively, which exposed face is capable of localized elasticdeformation so that the engaging means 30 may become entrapped and notwithdrawn without interference. The openings or localized elasticdeformations allow for entry of the engaging means 30 into the plane ofthe receiving surface, while the strands (or nondeformed material) ofthe receiving surface interposed between the openings (or deformedareas) prevent withdrawal or release of the fastening system 20 untildesired by the user or either the peel or shear strength of thefastening system 20 is otherwise exceeded. The plane of the receivingsurface may be flat or curved.

A receiving surface having strands or fibers, is said to be"complementary" if the openings between strands or fibers are sized toallow at least one engaging means 30 to penetrate into the plane of thereceiving surface, and the strands are sized to be engaged orintercepted by the engaging means 30. A receiving surface which islocally deformable is said to be "complementary" if at least oneengaging means 30 is able to cause a localized disturbance to the planeof the receiving surface, which disturbance resists removal orseparation of the fastening system 20 from the receiving surface.

Suitable receiving surfaces include reticulated foams, knitted fabrics,nonwoven materials, and stitchbonded loop materials, such as Velcrobrand loop materials sold by Velcro USA of Manchester, N.H. Aparticularly suitable receiving surface is stitchbonded fabric Number970026 sold by the Milliken Company of Spartanburg, S.C.

Referring back to FIG. 2 to examine the components of the fasteningsystem 20 in more detail, the substrate 24 of the fastening system 20should be strong enough to preclude tearing and separation betweenindividual prongs 22 of the fastening system 20, be a surface to whichthe prongs 22 will readily adhere and be capable of being joined to anarticle to be secured as desired by a user. As used herein the term"join" refers to the condition where a first member, or component, isaffixed, or connected to a second member or component, either directly;or indirectly, where the first member or component is affixed orconnected to an intermediate member, or component which in turn isaffixed, or connected, to the second member or component. Theassociation between the first member, or component, and the secondmember, or component, is intended to remain for the life of the article.The "substrate" is any exposed surface to which one or more prongs 22are joined.

The substrate 24 should also be capable of being rolled, to supportconventional manufacturing processes, flexible so that the substrate 24may be bent or flexed in a desired configuration, and able to withstandthe heat of the liquid prongs 22 being deposited thereon without meltingor incurring deleterious effects until such prongs 22 freeze. Thesubstrate 24 should also be available in a variety of widths. Suitablesubstrates 24 include knitted fabric, woven materials, nonwovenmaterials, rubber, vinyl, films, particularly polyolefinic films andpreferably kraft paper. White kraft paper having a basis weight of 0.08kilograms per square meter (50 pounds per 3,000 square feet) has beenfound suitable.

The base 26 is the generally planar portion of the prong 22 which isattached to the substrate 24 and is contiguous with the proximal end ofthe shank 28 of the prong. As used herein, the term "base" refers tothat portion of the prong 22 which is in direct contact with thesubstrate 24 and supports the shank 28 of the prong 22. It is notnecessary that a demarcation be apparent between the base 26 and theshank 28. It is only important that the shank 28 not separate from thebase 26 and that the base 26 not separate from the substrate 24 duringuse. The base 26 cross section should provide sufficient structuralintegrity, and hence area, for the desired peel and shear strengths ofthe fastening system 20, based on the density of the pattern of prongs22 and length of the shanks 28 of the individual prongs 22 and furtherprovide adequate adhesion to the substrate 24. If a longer shank 28 isutilized, the base 26 should generally be of greater cross sectionalarea to provide sufficient adhesion to the substrate 24 and adequatestructural integrity.

The shape of the footprint of the base 26 on the substrate 24 is notcritical, and may be amplified in any direction to provide greaterstructural integrity and thus a greater peel strength in that direction.As used herein, the term "footprint" refers to the planar contact areaof the base 26 on the substrate 24. The aspect ratio of the sides of thefootprint should not be too great, otherwise the prong 22 may beunstable when subjected to forces parallel to the shorter side of thefootprint. An aspect ratio of less than about 1.5:1 is preferred, and agenerally circular footprint is more preferred.

For the embodiment described herein, a base 26 having a footprint ofgenerally circular shape and approximately 0.76 millimeters to 1.27millimeters (0.030 to 0.050 inches) in diameter is suitable. If it isdesired to make the fastening system 20 have a greater peel or shearstrength in a particular direction, the cross sectional area of the base26 may be modified to amplify such direction, so that the strength andstructural integrity relative to the axis orthogonal to such directionincreases. This modification causes the prongs 22 to be stronger whenpulled in the amplified direction of the base 26.

The shank 28 is contiguous with the base 26 and projects outwardly fromthe base 26 and substrate 24. As used herein, the term "shank" refers tothat portion of the prong 22 which is intermediate of and contiguouswith the base 26 and the engaging means 30. The shank 28 provideslongitudinal spacing of the engaging means 30 from the substrate 24. Asused herein, the term "longitudinal" means in a direction having avector component away from the substrate 24, which direction increasesthe perpendicular distance to the plane of the substrate 24 at the base26 of the prong 22, unless otherwise-specified to be a direction havinga vector component towards such plane of the substrate 24.

Associated with the shank 28 and base 26 of each prong 22 is an origin36. The "origin" of the shank 28 is the point which may be thought of asthe center of the base 26, and is typically within the footprint of thebase 26. The origin 36 is found by viewing the prong 22, from the sideview. The "side view" is any direction radially towards the shank 28 andbase 26 which is also parallel to the plane of the substrate 24. If thefastening system 20 is manufactured by the process described and claimedbelow, it is preferred, but not necessary, that the prong 22 be viewedin the machine and cross-machine directions, relative to the travel ofthe substrate 24 through the nip 70, when determining the origin 36.

The lateral distance between the remote edges of the base 26 footprintfor the particular side view under consideration is found, and thisdistance is bisected, yielding the midpoint of the base 26 for suchview. When bisecting the footprint of the base 26 for the particularside view under consideration, minor discontinuities (such as fillets orasperities incident to the attachment to substrate 24) are ignored. Thispoint is the origin 36 of the shank 28.

The shank 28 makes an angle α with the plane of the substrate 24. Asused herein, the term "plane of the substrate" refers to the flat,planar surface of the substrate 24 at the base 26 of the principal prong22 under consideration. The angle α is determined as follows. The prong22 is viewed in profile. The "profile view" of the prong 22 is one oftwo particular side views and found as follows. The prong 22 is visuallyinspected from the side views such that the direction having the maximumlateral projection 38 becomes apparent. The "lateral projection" is thedistance taken laterally and parallel to the plane of the substrate 24from the center of the base 26 in such view, i.e. the origin 36 of theshank 28, to the projection of the furthest laterally remote point onthe prong 22 visible in such view when such point is longitudinally andperpendicularly projected downward to the plane of the substrate 24.

It will be apparent to one skilled in the art that the maximum lateralprojection 38 is that projection from the origin 36 to the outerperiphery of the shank 28 or engaging means 30. The side view of theprong 22 which maximizes the lateral projection 38 is the profile viewof such prong 22. It will also be apparent to one skilled in the artthat if the fastening system 20 is produced by the process described andclaimed below, and if the maximum lateral projection 38 is generallyoriented in the machine direction, then the profile view will begenerally oriented in the cross-machine direction. It will also beapparent that if the maximum lateral projection 38 is generally orientedin the cross-machine direction then the profile view will be generallyoriented in the machine direction. The side elevational view shown inFIG. 2 is one of the profile views of the prong 22. It will be furtherapparent to one skilled in the art that there is another profile view,generally 180° opposite from the profile view shown (so that the maximumlateral projection 38 is oriented towards the left of the viewer).Either of the two profile views is generally equally well suited for theprocedures and usages described hereinbelow.

The origin 36 of the shank 28 is found, as described above, with theprong 22 in the profile view. While still maintaining the prong 22 inthe profile view, an imaginary cutting plane 40--40, generally parallelto the plane of the substrate 24, is then brought into tangency with theperiphery of the prong 22 at the point or segment of the prong 22 havingthe greatest perpendicular distance from the plane of the substrate 24.This corresponds to the portion of the prong 22 having the highestelevation. The imaginary cutting plane 40--40 is then brought one-fourthof such greatest perpendicular distance closer to the substrate 24 fromthe point of highest elevation, so that the imaginary cutting plane40--40 intercepts the prong 22 at a longitudinal elevation three-fourthsof the perpendicular distance from the plane of the substrate 24.

The imaginary cutting plane 40--40 is then used to determine threepoints on the prong 22. The first point is that point where the cuttingplane intercepts the leading edge 42 of the prong 22 and is referred toas the 75% leading point 44. The "leading edge" is the apex of theperiphery of the shank 28 which longitudinally faces away from the planeof the substrate 24. The second point is disposed about 180° through thecenter of the prong 22 and is the point where the cutting plane 40--40intercepts the trailing edge 46 of the prong 22 and is referred to asthe 75% trailing point 48. The "trailing edge" is the apex of theperiphery of the shank 28 which longitudinally faces towards thesubstrate 24 and is generally oppositely disposed from the leading edge42. The straight line connecting these two points falls, of course,within the cutting plane 40--40 and is bisected to yield the midpoint 47of the imaginary cutting plane 40--40. A straight line is then drawnconnecting the midpoint 47 of the imaginary cutting plane 40--40 withthe origin 36 of the shank 28 at the base 26. The included angle α thisline defines relative to the plane of the substrate 24 is the angle α ofthe shank 28.

Alternatively stated, the angle α which the shank 28 makes relative tothe plane of the substrate 24 is the 90° complement of that anglefurthest from the perpendicular defined by the line, found in any sideview, connecting the cutting plane midpoint 47 and the origin 36. Hence,the smallest angle relative to the plane of the substrate 24 when thisline is viewed in any direction radially towards the shank 28, andparticularly the origin 36, which direction is generally parallel to theplane of the substrate 24 and orthogonal to the perpendicular is theangle α of the shank 28. It is to be recognized that when a prong 22having a maximum lateral projection 38 oriented in the machine directionis viewed approximately in the machine direction, or approximately 180°therefrom, or when a prong 22 having a maximum lateral projection 38oriented in the cross-machine direction is viewed approximately in thecross-machine direction, the apparent angle α of the shank 28 will beabout 90°. However, as discussed above, the angle α to be measured isthat which deviates furthest from the perpendicular and, therefore, isgenerally that angle α determined when the prong 22 is viewed inprofile, typically from about the cross-machine direction for a prong 22oriented in the machine direction, and from about the machine directionfor a prong 22 oriented in the cross-machine direction.

The angle α of the shank 28 may be generally perpendicular to the planeof the substrate 24, or is preferably oriented in an acute angularrelation relative thereto to provide increased peel strength in aparticular direction, which direction is generally parallel to themaximum longitudinal projection 38. However, the angle α of the shank 28should not deviate excessively from the perpendicular, otherwise afastening system 20 of more directionally specific shear strengthresults. For the embodiment described herein, a shank 28 having an angleα between about 45° and about 80°, preferably about 65°, works well. Ifthe angle of the shank 28 is less than about 80°, the shank 28 isconsidered to be nonperpendicularly oriented relative to the plane ofthe substrate 24 (without regard to lateral orientation).

The imaginary cutting plane 40--40 and profile view can also be utilizedto determine the angles of the leading edge 42 and the trailing edge 46relative to the plane of the substrate 24. To determine these angles,the 75% leading point 44 and 75% trailing point 48 are found asdescribed above. The base 26 leading point 50 is found as follows. Theline through the base 26 as viewed in profile is brought to intersectthe leading edge 42 of the shank 28. This intersection is the "baseleading point." As noted above, minor discontinuities in the shank 28near the base 26, incident to attachment to the substrate 24, are notconsidered when determining the base leading point 50. The 75% leadingedge 42 point is connected by a straight line to the base leading edge42 point. This straight line forms an included angle β_(L) relative tothe plane of the substrate 24 and opening in the direction of the origin36 and center of the shank 28. The angle β_(L) is referred to as theangle of the leading edge 42 or simply the leading edge angle.

The base trailing point 52 is generally disposed 180° from the baseleading point 50, through the center of the base 26, and found asfollows. The line through the footprint of the base 26 as viewed inprofile is brought to intersect the trailing edge 46 of the shank 28.This intersection is the "base trailing point." As noted above, minordiscontinuities in the shank 28 near the base 26, incident to attachmentto the substrate 24, are not considered when determining the basetrailing point 52. As described above, the 75% trailing point 48 isconnected with the base trailing point 52 by a straight line. Thisstraight line forms an included angle β_(T) relative to the plane of thesubstrate 24 and opening in the direction of the origin 36 and center ofthe shank 28. The included angle β_(T) is referred to as the angle ofthe trailing edge 46 or simply the trailing edge angle.

The leading edge 42 and trailing edge 46 included angles β_(L) and β_(T)define the parallelism of the sides of the shank 28. If the angles β_(L)and β_(T) of the leading and trailing edges 42 and 46 are notsupplementary to each other (do not add to an arithmetic sum of about180°) the sides of the shank 28 are said to be nonparallel. If the sidesof the shank 28 are nonparallel, the straight lines which define theangles β_(L) and β_(T) (connecting the base leading and trailing points50 and 52 with the 75% leading and trailing points 44 and 48respectively) intersect, either above or below the plane of thesubstrate 24. If the angles β_(L) and β_(T) of the leading and trailingedges 42 and 46 are unequal and the lines defining such angles intersectabove the plane of the substrate 24 (longitudinally outwardly of thebase 26), the prong 22 will converge from the base 26 towards the distalend and engaging means 30. Only if the angles β_(L) and β_(T) of theleading and trailing edges 42 and 46 have the same sense i.e., areoriented in the same direction, and supplementary magnitudes are theangles β_(L) and β_(T) of the leading and trailing edges 42 and 46determined to be equal and the sides of the shank 28 to be parallel.

A shank 28 having a leading edge 42 which forms a leading edge angleβ_(L) with the substrate of about 45°±30° is suitable. A trailing edge46 which forms a trailing edge angle β_(T) with the substrate of about65°±30° is suitable. A shank 28 having these angles β_(L) and β_(T) ofthe leading and trailing edges 42 and 46 works well with theaforementioned spectrum of included angles α of the shank 28 to yield atapered shank 28, advantageously oriented relative to the substrate 24to provide high shear and peel strengths without requiring excessiveprong material.

The foregoing measurements are easily made using a Model 100-00 115goniometer sold by Rame'-Hart, Inc. of Mountain Lakes, N.J. If moreprecise measurement is desired, it will be recognized by one skilled inthe art that determination of the profile view, origin 36, cutting plane40--40, leading angle β_(L), trailing angle β_(T), base points 50 and52, 75% points 44 and 48, and the angle α of the shank 28 can beadvantageously performed by making a photograph of the prong 22. A model1700 scanning electron microscope sold by Amray, Inc. of New Bedford,Mass. has been found to work well for this purpose. If necessary,several photographs may be taken to determine the maximum lateralprojection 38 and hence, either profile view.

The shank 28 should longitudinally project from the base 26 a distancesufficient to space the engaging means 30 from the substrate 24 at anelevation which allows the engaging means 30 to readily intercept orengage the strands of the receiving surface. A relatively longer shank28 provides the advantage that it can penetrate deeper into thereceiving surface and thereby allow the engaging means 30 to interceptor engage a greater number of strands or fibers. Conversely, arelatively shorter shank 28 length provides the advantage that arelatively stronger prong 22 results, but also provides correspondinglyless penetration into the receiving surface and may therefore beunsuitable for receiving surfaces such as wool or loosely stitchedbonded materials which have less densely packed strands or fibers.

If a knitted or woven material receiving surface is utilized, arelatively shorter shank 28 having a longitudinal length from thesubstrate 24 to the point or segment of highest elevation of about 0.5millimeters (0.020 inches), preferably at least about 0.7 millimeters(0.028 inches), is suitable. If a high loft material receiving surfacehaving a caliper greater than about 0.9 millimeters (0.035 inches) isutilized, a relatively longer shank 28 having a greater longitudinaldimension of at least about 1.2 millimeters (0.047 inches), preferablyat least about 2.0 millimeters (0.079 inches), is more suitable. As theshank 28 length increases, and shear strength correspondinglydiminishes, the density of the prongs 22 of the fastening system 20 maybe increased to compensate for such loss of shear strength.

As described above, the longitudinal length of the shank 28 determinesthe longitudinal spacing of the engaging means 30 from the substrate 24.The "longitudinal spacing" is the least perpendicular distance from theplane of the substrate 24 to the periphery of the engaging means 30. Foran engaging means 30 of constant geometry, the longitudinal spacing ofthe engaging means 30 from the substrate 24 becomes greater withincreasing longitudinal shank 28 length. A longitudinal spacing of atleast about twice the strand or fiber diameter of the intended receivingsurface, and preferably about 10 times as great as such fiber or stranddiameter provides good interception or engagement and retention of suchstrands or fibers by the engaging means 30 of the fastening system 20.For the embodiment described herein, a prong 20 having a longitudinalspacing of about 0.2 millimeters to about 0.8 millimeters (0.008 to 0.03inches) works well.

The shape of the cross section of the shank 28 is not critical. Thus theshank 28 may be of any cross section desired, according to theaforementioned parameters relating to the cross section of the base 26.The "cross section" is the planar area of any part of the prong 22 takenperpendicular to the shank 28 or the engaging means 30. As noted above,the shank 28 is preferably tapered to decrease in cross section as thedistal end of the shank 28 and engaging means 30 of the prong 22 arelongitudinally and laterally approximated. This arrangement provides acorresponding decrease in the moment of inertia of the shank 28 andengaging means 30 resulting in a prong 22 of more nearly constant stresswhen separation forces are applied to the fastening system 20, andthereby diminishes the quantity of superfluous materials incorporatedinto the prong 22.

To maintain the desired geometry over a wide range of prong 22 sizes, agenerally uniform ratio of cross sectional areas can be utilized toscale the prongs 22. One ratio which generally controls the overalltaper of the prong 22 is the ratio of the area of the cross section ofthe base 26 to the area of the cross section of the prong 22, at thehighest elevation of the prong 22. The phrase "highest elevation" refersto the that point or segment of the shank 28 or the engaging means 30having the greatest perpendicular distance from the plane of thesubstrate 24. Typically, prongs 22 having a base 26 cross sectional areato highest elevation cross sectional area ratio in the range of about4:1 to about 9:1 work well.

A generally circular shank 28 which tapers from a base 26 diameter, asdiscussed above, ranging from about 0.76 millimeters to about 1.27millimeters (0.030 to about 0.050 inches) to a highest elevationdiameter, of about 0.41 millimeters to about 0.51 millimeters (0.016 to0.020 inches) has been found suitable for the embodiment discussedherein. Specifically, a generally circular shaped cross section of about0.46 millimeters (0.018 inches) diameter at the highest elevationprovides a cross sectional area at highest elevation of about 0.17square millimeters (0.0003 square inches). A generally circular shapedbase 26 cross section of about 1.0 millimeters (0.040 inches) provides abase 26 cross sectional area of about 0.81 square millimeters (0.0013square inches). This structure results in a ratio of base 26 crosssectional area to highest elevation cross sectional area of about 5:1,which is within the aforementioned range.

The engaging means 30 is joined to the shank 28, and preferably iscontiguous with the distal end of the shank 28. The engaging means 30projects radially away and outwardly from the periphery of shank 28, andmay further have a vector component which longitudinally projects, i.e.towards or away from the substrate 24. As used herein the term "engagingmeans" refers to any protrusion lateral to the periphery of shank 28(other than minor asperities in the periphery of the shank 28), whichprotrusion resists separation or removal from a receiving surface. Theterm "periphery" means the outer surface of the prong 22. The term"radially" means from or towards the perpendicular to the substrate 24,which perpendicular passes through the origin 36 which is generallycentered within the footprint of the base 26.

Particularly, the lateral protrusion has a vector component parallel toand facing towards the plane of the substrate 24. It is to be recognizedthat the engaging means 30 and shank 28 may have both lateral andlongitudinal vector components. It is not important that a sharplydefined terminus of the shank 28 distal end be apparent, or that ademarcation between the shank 28 and engaging means 30 be discernible atall. It is only necessary that a longitudinally oriented face of theshank 28 periphery be interrupted so that the engaging means 30 has aface with a vector component parallel to and facing the plane of thesubstrate

The engaging means 30 may have a greater lateral projection 38 than theshank 28, or vice-versa, as desired. As illustrated in the figures, theengaging means 30 is preferably generally arcuate and may have areentrant curve. If the engaging means 30 has a reentrant curve, theengaging means 30 includes a segment which longitudinally approximatesthe substrate 24 at the base 26 or a location laterally spaced from thebase 26. This segment is laterally directed towards the shank 28,although the segment need not be radially directed towards the origin36.

The engaging means 30 of each prong 22 of the fastening system 20 maylaterally extend substantially in the same direction, if a relativelyunidirectionally oriented peel strength is desired, or may be randomlyoriented to provide substantially isotropic peel strengths in anylateral direction. The engaging means 30 may be hook-shaped tines whichproject substantially from one side of the shank 28, defining agenerally convex outline, and penetrate the opening of the receivingsurface to intercept the strands or fibers of the receiving surface atthe inner radius of curvature 54 of the engaging means 30. Theinterference between the engaging means 30 and strands or fibers of thereceiving surface prevents release of the fastening system 20 from thereceiving surface until the peel strength or shear strength of thefastening system 20 is exceeded. The engaging means 30 should notradially project too far in the lateral direction, otherwise theengaging means 30 may not penetrate the opening of the receivingsurface. The cross section of the engaging means 30 should be sized topenetrate the openings of the receiving surface. The cross sectionalarea and geometry of the engaging means 30 are not critical, so long asthe engaging means 30 has structural integrity which provides sufficientshear and bending strengths to accommodate the desired peel and shearstrengths of a fastening system 20 having an array of prongs 22 of agiven density. For the embodiment described herein, a hook-shaped tineengaging means 30 having a maximum lateral projection 38 from the centerof the base 26 to the remote lateral periphery of about 0.79 millimetersto about 0.90 millimeters (0.03 to 0.04 inches) is suitable.

The array of prongs 22 may be of any pattern and density as desired, toachieve the peel and shear strengths required for the particularapplication of the fastening system 20. Generally as the array densityincreases, peel strength and shear strength proportionately increase ina linear fashion. The individual prongs 22 should not be so closelyspaced as to interfere with and prevent the engaging means 30 of theadjacent prongs 22 from intercepting strands or fibers of the receivingsurface. If the prongs 22 are too closely spaced, compacting or mattingof the receiving surface strands or fibers may occur, occluding theopenings between the strands or fibers. Conversely, the prongs 22 shouldnot be so distantly spaced as to require an excessive area of substrate24 to provide a fastening system 20 of adequate shear and peelstrengths.

It is advantageous to dispose the prongs 22 in rows, so that each prong22 is generally equally spaced from the adjacent prong 22. The rows aregenerally oriented in the machine direction and cross-machine directionaccording to the manufacturing process described and claimed below.Generally, each machine direction and cross-machine direction row ofprongs 22 should be equally spaced from the adjacent machine directionand cross-machine direction rows of prongs 22, to provide a generallyuniform stress field throughout the fastening system 20 and thereceiving surface when separation forces are applied to the fasteningsystem 20 and the receiving surface.

As used herein the term "pitch" refers to the distance, measured eitherin the machine direction or cross-machine direction, between the centersof the footprints of the bases 26 of prongs 22 in adjacent rows.Typically a fastening system 20 having an array of prongs 22 with apitch ranging from about 1.02 millimeters to about 5.08 millimeters(0.04 to 0.20 inches) in both directions is suitable, with a pitch ofabout 2.03 millimeters (0.08 inches) being preferred. Adjacentcross-machine direction rows are preferably offset approximatelyone-half pitch in the cross-machine direction to double the distance inthe machine direction between the adjacent cross-machine direction rows.

The prongs 22 may be thought of as disposed in a matrix on a one squarecentimeter grid having an array of prongs 22 with about 2 to about 20rows of prongs 22 per centimeter (5 to 50 rows per inch) in both themachine and cross-machine directions, preferably about 9 rows of prongs22 per centimeter (23 rows per inch) in each direction. This grid willresult in a fastening system 20 having about 4 to about 400 prongs persquare centimeter (25 to 2500 prongs per square inch) of substrate 24.

The fastening system 20 prongs 22 may be made of any thermally sensitivematerial which is stable and shape retaining when solid, but not sobrittle that failure occurs when the fastening system 20 is subjected toseparation forces. As used herein, "thermally sensitive" means amaterial which gradually changes from the solid state to the liquidstate upon the application of heat. Failure is considered to haveoccurred when the prong 22 has fractured or can no longer sustain areaction in the presence of and when subjected to separation forces.Preferably the material has an elastic tensile modulus, measuredaccording to ASTM Standard D-638, of about 24,600,000 to about31,600,000 kilograms per square meter (35,00 to 45,000 pounds per squareinch).

Further, the prong material should have a melting point low enough toprovide for easy processing and a relatively high viscosity to provide atacky and tough consistency at temperatures near the material meltingpoint, so that the shanks 28 may be stretched and the engaging means 30easily formed according to the method of manufacture recited below. Itis also important that the prongs 22 be viscoelastic, to allow for morevariation in the parameters affecting prong 22 structure, andparticularly the geometry of the engaging means 30. Material having acomplex viscosity ranging from about 20 to about 100 Pascal seconds atthe temperature of application to the substrate 24 is suitable.

The viscosity may be measured with a Rheometrics Model 800 MechanicalSpectrometer using the dynamic operating mode at a 10 Hertz samplingfrequency and 10% material strain. A disk and plate type geometry ispreferred, particularly with a disk having a radius of about 12.5millimeters and a gap of about 1.0 millimeters between the disk andplate.

The prongs 22 are preferentially comprised of a thermoplastic material.The term "thermoplastic" refers to uncrosslinked polymers of a thermallysensitive material which flows under the application of heat orpressure. Hot melt adhesive thermoplastics are particularly well suitedto manufacture/the fastening system 20 of the present invention,particularly in accordance with the process described and claimed below.As used herein the phrase "hot melt adhesive" refers to thermoplasticcompounds, normally solid at room temperature, which become fluid atelevated temperatures and which are applied in the molten state.Examples of hot melt adhesives may be found in the "Handbook OfAdhesives", Second Edition by Irving Skeist, published in 1977 by VanNostrand Reinhold Company, 135 West 50th Street, New York, N.Y., 10020,which is incorporated herein by reference. Polyester and polyamide hotmelt adhesives are particularly suitable and preferred. As used herein,the terms "polyester" and "polyamide" mean chains having repeating esterand amide units respectively.

If a polyester hot melt adhesive is selected, an adhesive having acomplex viscosity of about 23±2 Pascal seconds at about 194° C. has beenfound to work well. If a polyamide hot melt adhesive is selected, anadhesive having a complex viscosity of about 90±10 Pascal seconds atabout 204° C. has been found to work well. A polyester hot melt adhesivemarketed by the Bostik Company of Riddleton, Mass. as No. 7199 has beenfound to work well. A polyamide hot melt adhesive marketed by the HenkelCompany of Kankakee, Ill. under the tradename Macromelt 6300 has beenfound to work well.

In a second embodiment of the fastening system 20', illustrated by FIG.3, the engaging means 30' may be generally semispherically (mushroom)shaped. The term "semispherical" means a generally round shape,protruding in multiple directions and is inclusive of hemispheres andspheres, but not limited to regular shapes. This geometry, particularlythe generally spherically shaped engaging means 30' structure, providesthe advantage that less disturbance to the strands of the receivingsurface typically occurs when the engaging means 30' is removed from thereceiving surface. This causes less visible damage to the receivingsurface, allowing it to be reused a greater number of times. If thesemispherically shaped engaging means 30' is selected, the shank 28' ispreferably more nearly orthogonal to the plane of the substrate 24', toallow easier penetration into the openings of the receiving surface andto reduce damage to the receiving surface as the engaging means 30' isreleased from the receiving surface. A shank 28' having an angle α' ofabout 70° to about 90° is suitable.

To provide a prong 22' of the proper proportions and having a generallysemispherical engaging means 30', the engaging means 30' should radiallyprotrude from the circumference of the shank 28' a lateral distancesufficient to intercept the strands of the receiving surface, but notprotrude so far that the mass of the engaging means 30' is unable to berigidly supported by the shank 28' or the shank 28' is otherwiseunstable. As the angle α' of the shank 28' decreases, i.e. deviatesfurther from the perpendicular, the mass of the engaging means 30'relative to the shank 28' structural integrity and cross sectional areabecomes more critical.

A tapered shank 28', having the base 26' to highest elevation crosssectional area and diameter ratios described above, and an angle α' ofthe shank 28' of about 80° works well. It is to be recognized thehighest elevation measurements are to be taken from the highestelevation of the shank 28' and not from the engaging means 30'.

For an embodiment, as illustrated in FIG. 3, which does not have asmooth transition from the shank 28' to the engaging means 30', and forwhich the demarcation between the shank 28' and engaging means 30' iseasily determined, the imaginary cutting plane 40'--40' is three-fourthsof the perpendicular distance from the plane of the substrate 24' to theplane tangent to the point of the engaging means 30' which islongitudinally closest to the plane of the substrate 24'. The cuttingplane 40'--40' is then used to determine the angle α' of the shank 28',the leading edge angle β_(L) ' and trailing edge angle β_(T) ' asdescribed above.

The engaging means 30' should radially project, in each lateraldirection, from the periphery of the distal end 29' of the shank 28' atleast about 25 percent of the diameter of the distal end 29' of theshank 28, and preferably at least about 38 percent of such diameter.Alternatively stated, if the diameter of the distal end 29' of shank 28'is normalized to 1.0, the diameter of the engaging means 30' should beat least 1.5, and preferably at least 1.75 times the diameter of thedistal end 29' of the shank 28'. Furthermore, the diameter of the base26' should be about 2.0 times the diameter of the distal end 29' of theshank 28'. The shank 28' height should be about 1.5 to about 2 times thediameter of the distal end 29' of the shank 28', to properlylongitudinally space the engaging means 30' from the substrate 24'. Thelongitudinal dimension of the engaging means 30' may range from about0.5 to about 1.5 times the diameter of the distal end 29' of the shank28'.

The fastening system 20' of FIG. 3 is made by heating the engaging means30 and distal end of the fastening system 20 of FIG. 2 to at least themelting point. This is accomplished by bringing the engaging means 30and distal ends of the prongs 22 to a heat source longitudinallydirected toward the plane of the substrate so that the base 26' and theproximal end of the shank 28' are not heated to at least the meltingpoint. A suitable method is to bring the highest elevation of the prongto within about 3.3 millimeters to about 10.1 millimeters (0.1 to 0.4inches) of a heat source, such as a hot wire heated to about 440° C.

The leading edge angle β_(L) ' and trailing edge angle β_(T) ' of theprong 22' will be similar to that of the corresponding hook-shaped tinestyle engaging means prong 22, from which the semispherically shapedengaging means style prong 22' was formed. This occurs because the angleα' of the shank 28' and leading edge and trailing edge angles β_(L) 'and β_(T) ' do not substantially change as the engaging means 30 of FIG.2 is heated and melted to flow into the engaging means 30' of FIG. 3.

For the aforementioned Milliken 970026 receiving surface, the engagingmeans 30' of FIG. 3 should preferably have a lateral and longitudinaldimension of about 0.029 millimeters to about 0.032 millimeters (0.001inches), and be disposed on a shank 28' having a base 26' diameter ofabout 0.30 millimeters to about 0.045 millimeters (0.012 to 0.002inches) and a diameter at the distal end 29' of about 0.016 millimetersto about 0.020 millimeters (0.0006 to 0.0007 inches). The distal end 29'of the shank 28' should be disposed between about 0.44 millimeters andabout 0.50 millimeters (0.017 inches to 0.020 inches) above the plane ofthe substrate 24', and the engaging means 30' should have a lateralprojection 38' of about 0.56 millimeters to about 0.70 millimeters(0.022 to 0.028 inches), preferably about 0.64 millimeters (0.025inches).

PROCESS OF MANUFACTURE

The fastening system 20 according to the present invention may bemanufactured using a modified gravure printing process. Gravure printingis well known in the art as illustrated by U.S. Pat. No. 4,643,130issued Feb. 17, 1988, to Sheath et al. and incorporated herein byreference to illustrate the general state of the art. Referring to FIG.4, the substrate 24 is passed through the nip 70 formed between tworolls, a print roll 72 and a backing roll 74. The rolls 72 and 74 havesubstantially mutually parallel centerlines disposed generally parallelto the plane of the substrate 24. The rolls 72 and 74 are rotated aboutthe respective centerlines and have generally equal surface velocities,in both magnitude and direction, at the nip point 70. If desired, boththe print roll 72 and the backing roll 74 may be driven by an externalmotive force (not shown), or one roll driven by external motive forceand the second roll driven by frictional engagement with the first roll.An alternating current electric motor having an output of about 1,500watts provides adequate motive force. By rotating, the rolls 72 and 74actuate a depositing means for depositing the prongs 22 onto thesubstrate 24.

The depositing means should be able to accommodate the temperature ofthe material of prongs 22 in the liquid state, provide substantiallyuniform pitch between the prongs 22 in both the machine andcross-machine directions and yield the desired density of prongs 22within the array. Also, the depositing means should be able to produceprongs having various diameters of the base 26 and heights of the shank23. The print roll 72, specifically, provides for the depositing meansto deposit the prongs 22 on the substrate 24 in the desired array,discussed above, (or other pattern) according to the presentmanufacturing process. The phrase "depositing means" refers to anythingwhich transfers liquid prong material from a bulk quantity to thesubstrate 24 in dosages corresponding to individual prongs 22. The term"deposit" means to transfer prong material from the bulk form and dosesuch material onto the substrate 24 in units corresponding to individualprongs 22.

One suitable depositing means for depositing prong material onto thesubstrate 24 is an array of one or more cells 76 in the print roll 72.As used herein the term "cell" refers to any cavity, or other componentof the print roll 72, which transfers prong material from a source tothe substrate 24 and deposits this material onto the substrate 24 indiscrete units.

The cross sectional area of the cell 76, taken at the surface of theprint roll 72, generally corresponds with the shape of the footprint ofthe base 26 of the prong 22. The cross section of the cell 76 should beapproximately equal to the desired cross section of the base 26. Thedepth of the cell 76, in part, determines the longitudinal length of theprong 22, specifically the perpendicular distance from the base 26 tothe point or segment of highest elevation. However, as the depth of thecell 76 increases to more than approximately 70 percent of the diameterof the cell 76, the longitudinal dimension of the prong 22 generallyremains constant. This is because not all of the liquid prong materialis pulled out of the cell 76 and deposited on the substrate 24. Due tothe surface tension and viscosity of the liquid prong material, some ofit will remain in the cell 76 and not be transferred to the substrate24.

For the embodiment described herein, a blind, generally cylindricallyshaped cell 76 having a depth between about 50 and about 70 percent ofthe diameter is adequate. If desired, the cell 76 may be somewhatfrustoconically tapered in shape to accommodate conventionalmanufacturing processes, such as chemical etching.

If frustoconically shaped, the included angle of the taper of the cell76 should be no more than about 45° to produce the preferred taper ofthe shank 28 and yield the base to highest elevation ratios discussedabove. If the taper of the cell 76 has a greater included angle, a prong22 having too much taper may result, If the included angle is too small,or the cell 76 is cylindrical, a shank 28 of generally uniform crosssection may result, and thereby have areas of higher stress. For theembodiment described herein a cell 76 having an included angle of about45°, a diameter at the roll periphery of about 0.89 millimeters to about1.22 millimeters (0.035 to 0.048 inches) and a depth ranging from about0.25 millimeters to about 0.51 millimeters) 0.01 to 0.02 inches producesa suitable prong 22.

The print roll 72 and backing roll 74 should be compressed, coincidentwith the line connecting the centerlines of the rolls, to press theadhesive from the cells 76 in the print roll 72 onto the substrate 24and to provide sufficient frictional engagement to drive the opposingroll if it is not externally driven. The backing roll 74 should besomewhat softer and more compliant than the print roll 72 to providecushioning of the prong material as it is deposited on the substrate 24from the print roll 72. A backing roll 74 having a rubber coating with aShore A durometer hardness of about 40 to about 60 is suitable. Therolls 72 and 74 may be pressed together with such a force that animpression in the machine direction of about 6.4 millimeters to about12.7 millimeters (0.25 to 0.50 inches) is obtained. As used herein theterm "impression" refers to the contact area of the softer roll on thesubstrate 24 as it passes through the nip 70.

The print roll 72 is preferably heated to prevent solidification of theprongs 22 during transfer from the source through the deposition on thesubstrate 24. Generally a print roll 72 surface temperature near thesource material temperature is desired. A print roll 72 temperature ofabout 197° C. has been found to work well with the polyester hot meltadhesive marketed by the Bostik Company of Riddleton, Mass. as No. 7199.

It is to be recognized that a chill roll may be necessary if thesubstrate 24 is adversely affected by the heat transferred from theprong material. If a chill roll is desired, it may be incorporated intothe backing roll 74 using means well known to one skilled in the art.This arrangement is often necessary if a polypropylene, polyethylene orother polyolefinic substrate 24 is used.

The material used to form the individual prongs 22 must be kept in asource which provides for the proper temperature to apply the prongs 22to the substrate 24. Typically, a temperature slightly above the meltingpoint of the material is desired. The material is considered to be at orabove the "melting point" if the material is partially or wholly in theliquid state. If the source of the prong material is kept at too high atemperature, the prong material may not be viscous enough and mayproduce engaging means 30 which laterally connect to the prongs 22adjacent in the machine direction. If the material temperature is veryhot, the prong 22 will flow into a small, somewhat semisphericallyshaped puddle and an engaging means 30 will not be formed. Conversely,if the source temperature is too low, the prong material may nottransfer from the source to the means for depositing the material or,subsequently, may not properly transfer from the depositing means 76 tothe substrate 24 in the desired array or pattern. The source of thematerial should also impart a generally uniform cross-machine directiontemperature profile to the material, be in communication with the meansfor depositing the adhesive material onto the substrate 24 and easily bereplenished or restocked as the prong material becomes depleted.

A suitable source is a trough 80, substantially coextensive of thatportion of the cross-machine dimension of the print roll 72 which hascells 76 and adjacent thereto. The trough 80 has a closed end bottom, anoutboard side and ends. The top may be open or closed as desired. Theinboard side of the trough 80 is open, allowing the liquid materialtherein to freely contact and communicate with the circumference of theprint roll 72.

The source is externally heated by known means (not shown) to maintainthe prong material in a liquid state and at the proper temperature. Thepreferred temperature is above the melting point but below that at whicha significant loss of viscoelasticity occurs. If desired, the liquidmaterial inside the trough 80 may be mixed or recirculated to promotehomogeneity and an even temperature distribution.

Juxtaposed with the bottom of the trough 80 is a doctor blade 82 whichcontrols the amount of prong material applied to the print roll 72. Thedoctor blade 82 and trough 80 are held stationary as the print roll 72is rotated, allowing the doctor blade 82 to wipe the circumference ofthe roll 72 and scrape any prong material which is not disposed withinthe individual cells 76 from the roll 72 and allows such material to berecycled. This arrangement allows prong material to be deposited fromthe cells 76 to the substrate 24 in the desired array, according to thegeometry of the cells 76 on the circumference of the print roll 72. Asseen in FIG. 4, the doctor blade 82 is preferentially disposed in thehorizontal plane, particularly the horizontal apex of the print roll 72,which apex is upstream of the nip point 70.

After being deposited onto the substrate 24, the prongs 22 are severedfrom the print roll 72 and the depositing means 76 by a severing meansfor severing 78 the prongs 22 into the engaging means 30 of thefastening system 20 and a moil. As used herein the term "moil" refers toany material severed from the prong 22 and which does not form part ofthe fastening system 20.

The severing means 78 should be adjustable to accommodate various sizesof prongs 22 and lateral projections 38 of engaging means 30 and alsoprovide uniformity throughout the cross-machine direction of the array.The term "severing means" refers to anything which longitudinallyseparates the moil from the fastening system 20. The term "sever" refersto the act of dividing the moil from the fastening system 20 asdescribed above. The severing means 78 should also be clean and shouldnot rust, oxidize or impart corrodents and contaminates (such as moilmaterial) to the prongs 22. A suitable severing means is a wire 78disposed generally parallel to the axis of the rolls 72 and 74 andspaced from the substrate 24 a distance which is somewhat greater thanthe perpendicular distance from the highest elevation of the solidifiedprong 22 to the substrate 24.

Preferably the wire 78 is electrically heated to prevent build-up of themolten prong material on the severing means 78, accommodate any coolingof the prongs 22 which occurs between the time the prong material leavesthe heated source and severing occurs and to promote lateral stretchingof the engaging means 30. The heating of the severing means 78 shouldalso provide for uniform temperature distribution in the cross-machinedirection, so that an array of prongs 22 having substantially uniformgeometry is produced.

Generally, as the prong material temperature increases a relativelycooler hot wire 78 temperature severing means can be accommodated. Also,as the speed of the substrate 24 is decreased, less frequent cooling ofthe hot wire 78 occurs as each prong 22 and moil are severed, making arelatively lower wattage hot wire 78 more feasible at the sametemperatures. It should be recognized that as the temperature of the hotwire 78 is increased a prong 22 having a generally shorter shank 28length will result. Conversely, the shank 28 length and lateral lengthof the engaging means 30 will be increased in inverse proportion as thetemperature of the hot wire 78 is decreased. It is not necessary thatthe severing means 78 actually contact the prong 22 for severing tooccur. The prong 22 may be severed by the radiant heat emitted from thesevering means 78.

For the embodiment described herein a round cross sectionnickel-chromium wire 78, having a diameter of about 0.51 millimeters(0.02 inches) heated to a temperature of about 343° C. to about 416° C.has been found suitable. It will be apparent that a knife, laser cuttingor other severing means 78 may be substituted for the hot wire 78described above.

It is important that the severing means 78 be disposed at a positionwhich allows stretching of the prong material to occur prior to theprong 22 being severed from the moil. If the severing means 78 isdisposed too far from the plane of the substrate 24, the prong materialwill pass underneath the severing means 78 and not be intercepted by it,forming a very long engaging means 30 which will not be properly spacedfrom the substrate 24 or adjacent prongs 22. Conversely, if the severingmeans 78 is disposed too close to the plane of the substrate 24, thesevering means 78 will truncate the shank 28 and an engaging means 30may not be formed.

A hot wire severing means 78 disposed approximately 14 millimeters to 22millimeters (0.56 to 0.88 inches), preferably about 18 millimeters (0.72inches) in the machine direction from the nip point 70, approximately4.8 millimeters to 7.9 millimeters (0.19 to 0.31 inches), preferablyabout 6.4 millimeters (0.25 inches) radially outward from the backingroll 74 and approximately 1.5 millimeters to approximately 4.8millimeters (0.06 to 0.19 inches), preferably about 3.3 millimeters(0.13 inches) radially outwardly from the print roll 72 is adequatelypositioned for the process of manufacture disclosed herein.

In operation, the substrate 24 is transported in a first directionrelative to the depositing means 76. Rote particularly, the substrate 24is transported through the nip 70, preferentially drawn by a take-uproll (not shown). This provides a clean area of substrate 24 forcontinuous deposition of prongs 22 and removes the portions of thesubstrate 24 having prongs 22 deposited thereon. The direction generallyparallel to the principal direction of transport of the substrate 24 asit passes through the nip 70 is referred to as the "machine direction."The machine direction, as indicated by the arrow 75 of FIG. 4, isgenerally orthogonal the centerline of the print roll 72 and backingroll 74. The direction generally orthogonal to the machine direction andparallel to the plane of the substrate 24 is referred to as the"cross-machine direction."

The substrate 24 may be drawn through the nip 70 at a speedapproximately 2% to approximately 10% greater than the surface speed ofthe rolls 72 and 74. This is done to minimize bunching or puckering ofthe substrate 24 near the means for severing 78 the prongs 22 from themeans for depositing the prong material on the substrate 24. Thesubstrate 24 is transported through the nip 70 in the first direction atabout 3 to about 31 meters per minute (10 to 100 feet per minute).

The angle of the shank 28 can be influenced by the rate of transport ofthe substrate 24 past the nip 70. If prongs 22 having a shank angle αmore nearly perpendicular to the substrate 24 is desired, a slower rateof transport of the substrate 24 in the first direction is selected.Conversely, if the rate of transport is increased, the angle α of theshank 28 decreases and an engaging means 30 have a greater lateralprojection 38 will result.

If desired, the substrate 24 may be inclined at an angle γ,approximately 35° to approximately 55°, preferably about 45°, from theplane of the nip 70 towards the backing roll 74 to utilize theviscoelastic nature of the prong material and properly orient theengaging means 30 in the lateral direction, as well as longitudinaldirection. This arrangement also provides a greater force to extract theprong material from the cell 76 and to pull the prong 22 away from theprint roll 72. The angle γ from the plane of the nip 70 should beincreased as a lesser angle α of the shank 28 is desired. Also,increasing the angle γ of deviation from the plane of the nip 70 has aweak, but positive effect to produce engaging means 30 having a greaterlateral projection 38.

After depositing prong material from the cell 76 onto the substrate 24,the rolls 72 and 74 continue rotation, in the directions indicated bythe arrows 75 of FIG. 4. This results in a period of relativedisplacement between the transported substrate 24 and the cells 76during which period (prior to severing) the prong material bridges thesubstrate 24 and print roll 72. As relative displacement continues, theprong material is stretched until severing occurs and the prong 22separated from the cell 76 of the print roll 72. As used herein the term"stretch" means to increase in linear dimension, at least a portion ofwhich increase becomes substantially permanent for the life of thefastening system 20.

As discussed above, it is also necessary to sever the individual prongs22 from the print roll 72 as part of the process which forms theengaging means 30. When severed, a prong 22 is longitudinally dividedinto two parts, a distal end and engaging means 30 which remain with thefastening system 20 and a moil (not shown) which remains with the printroll 72 and may be recycled, as desired. After the prongs 22 are severedfrom the moil, the fastening system 20 is allowed to freeze prior tocontact of the prongs 22 with other objects. After solidification of theprongs 22, the substrate 24 may be wound into a roll for storage asdesired.

A nonlimiting illustration of the process shows the prong material to bedisposed in the trough 80 and heated by means commonly known to oneskilled in the art, to a temperature somewhat above the melting point.If a polyester resin hot melt adhesive is selected, a materialtemperature of approximately 177°-193° C., preferably about 186° C. hasbeen found suitable. If a polyamide resin is selected, a materialtemperature of approximately 193°-213° C., preferably about 200° C. hasbeen found suitable. A one side bleached kraft paper substrate 24 about0.008 to about 0.15 millimeters (0.003 to 0.006 inches) in thicknessworks well with hot melt adhesive prongs 22. The prongs 22 are joined tothe bleached side of the kraft paper substrate 24.

For the illustrated operation described herein, print roll 72 having anarray of about 5 cells 76 per centimeter (13 cells 76 per inch) in boththe machine direction and cross-machine directions, yielding a grid ofabout 26 cells 76 per square centimeter (169 cells 76 per square inch),is suitable. This grid density may be advantageously used with a printroll 72 having a diameter of about 16 centimeters (6.3 inches), withcells 76 about 1 millimeter (0.045 inches) in diameter and about 0.8millimeters (0.030 inches) deep. A backing roll 74 having a diameter ofabout 15.2 centimeters (6.0 inches) and vertically registered has beenfound to work well with the aforementioned print roll 72. The rate oftransport of the substrate 24 is about 3.0 meters per minute (10 feetper minute).

A nickel-chromium hot wire 78 having a diameter of about 0.5 millimeters(0.02 inches) disposed approximately 18 millimeters (0.72 inches) fromthe nip point 70 in the machine direction, approximately 0.3 millimeters(0.13 inches) radially outwardly from the print roll 72 andapproximately 6.4 millimeters (0.25 inches) radially outwardly from thebacking roll 74 is heated to a temperature of about 382° C. Thefastening system 20 produced by this operation is substantially similarto that illustrated by FIG. 1, which fastening system 20 may beadvantageously incorporated into the illustrative article of usediscussed below.

Without being bound by any particular theory, it is believed that thegeometry of the engaging means 30 is governed by the elastic propertiesof the hot melt adhesive used to make the prong 22 and the difference inthe temperature between the trailing edge 46 and the leading edge 42 ofthe prong 22. The trailing edge 46 of the prong 22 is shielded andinsulated from the heat originating from the severing means 78.Conversely, the leading edge 42 is directly exposed to the heat of thesevering means 78, which causes the leading edge 42 to solidify orfreeze after the trailing edge 46. This causes elongation of the leadingedge 42 and contraction of the trailing edge 46, relative to each other.As this temperature difference is increased, a relatively longerengaging means 30 is formed.

If desired, a fastening system 20 having relatively very small prongs 22(not shown) may be made by forming a natural pattern from the print roll72. As used herein, the term "natural pattern" refers to array of prongs22 resulting from a print roll 72 which does not have cells 76 disposedthereon, but instead which utilizes the surface of the roll 72 as thedepositing means 76. Thus, the pattern of prongs 22 is formed by theclearance between the doctor blade 82 and the print roll 72, and to alesser extent by the surface finish of the print roll 72.

The doctor blade 82 should be adjusted to provide about a gap of about0.03 millimeters to about 0.08 millimeters (0.001 to 0.003 inches) inradial clearance from the print roll 72. To form a natural pattern, thevery small sized prongs 22 resulting from such a print roll 72 areadvantageously utilized with a reticulated foam receiving surface thatdoes not have strands and openings therebetween, but rather incurslocalized elastic deformations which resist separation of the fasteningsystem 20.

Referring to FIG. 5, if a fastening system 20" of more nearly isotropicpeel strength is desired, such a fastening system 20" may be formed bymodifying the fastening system 20 of FIG. 1 through a second stagedifferential temperature process. As illustrated in FIG. 5, thefastening system 20 of FIG. 1 is further processed to provide shanks 28"with engaging means 30" which radially extend from the shanks 28" invarious lateral directions of a generally random orientation. The phrase"random orientation" means having lateral projections 38" and profileviews which significantly deviate in direction from those of the nearbyprongs 22".

Without being bound by any particular theory, it is believed that thisstructure is accomplished by establishing a temperature differentialbetween the profile surfaces or leading surfaces 42 and the trailingsurfaces 46 of the prongs 22 of the fastening system 20 of FIG. 1, andthat such temperature differential may be enhanced by radiation orpreferably convection.

It is also believed that as a result of attaining a temperaturedifferential of the leading surface 42" or the profile surfaces relativeto the trailing surface 46", the engaging means 30" will substantiallychange or even reverse the orientation of lateral projection 38",providing a prong 22" which is oriented in a direction other than thatwhich occurred when initially cooled or frozen. The differentialtemperature may be established by any source known to one skilled in theart, such as a heated wire or metal element, and preferably an air gun84, disposed above the prongs 22" and capable of providing a directedtemperature differential to the fastening system 20".

It is desired that the directed temperature differential source directan air current towards the fastening system 20" within about ±90° of thefirst direction of substrate 24" travel, which is the machine direction.As used herein, the phrase "+90° of the first direction" means adirection having a vector component generally perpendicular to orgenerally counter to the first direction of travel of the substrate 24"and is inclusive of the direction generally opposite the first directionof travel.

If the directed temperature differential source 84 is disposed at anangle of about 180° relative to the first direction of travel of thesubstrate 24", the source 84 is directed towards the leading surfaces42" of the prongs 22" of the fastening system 20", and generallyopposite the machine direction of the process described and claimedherein. Directing the temperature differential of source 84 directlytowards the leading surface 42" of a prong 22" will result in thelateral projection 38" of the engaging means 30" rotating, to change theorientation of the lateral projection about 180°. Prongs 22" disposedsomewhat to the side, i.e. in the cross-machine direction, of thedirected temperature differential source 84 will not have the engagingmeans 30" rotated about 180°, but instead engaging means 30" more nearlyrotated about 90°. Thus, it is apparent that a directed temperaturedifferential source 84 oriented in the cross-machine direction willprovide a fastening system 20" having prongs 22" with various lateralorientations in the cross-machine direction according to the prong 22"position relative to the temperature differential source 84.

An air gun 84 discharging air at a temperature of about 88° C. at adistance of about 46 centimeters (18 inches) from the substrate 24" is asuitable differential temperature source. A 133-348 series heat gun soldby the Dayton Electric Manufacturing Company of Chicago, Ill. orientedat about 45° relative to the plane of the substrate 24" and disposedabout 46 centimeters (18 inches) from the prongs produces a fasteningsystem 20" pattern substantially similar to that shown in FIG. 5. Itwill be apparent to one skilled in the art that a one or more hot wiresdisposed above the prongs 22" and oriented in the machine direction willproduce a fastening system 20" having cross machine directionallyoriented engaging means 30" in a regular, somewhat striped pattern.

Without being bound by any theory, it is believed that the change inorientation of the engaging means 30" occurs due to the cooling of theprofile surfaces or the leading surface 42" of the prong 22" relative tothe trailing surface 46", which may occur if the temperature of thedischarged air from the directed temperature source differential source84 is less than the temperature of the periphery of such profilesurfaces or leading surface 42". The temperature differential resultingfrom the cooling causes contraction of the portion of the prong 22"towards which the temperature differential source 84 is directed. Thiscontraction may result in a change in the orientation of the engagingmeans 30" and lateral projection 38", due to the differential cooling ofthe leading surface 42" relative to the trailing surface 46". Withoutbeing bound by further theory, it is believed that relief of residualstresses which occur during cooling may influence the change inorientation of the lateral projection 38".

It will be further apparent to one skilled in the art that othervariations are feasible. For example, a prong 22 having an engagingmeans 30 protruding in more than one direction may be formed or freeformed prongs 22 may be produced by commonly known methods other thangravure printing. If desired, only one roll may be utilized in themanufacturing process, providing the substrate 24 contacts at leastabout 180' of the periphery of such roll.

It is frequently desirable to have a fastening system 20 of the presentinvention with the maximum lateral projection 38 of the prongs 22oriented in a direction other than the machine direction. For example,when using the present invention as the fastening means of a disposablediaper, it is desirable that the maximum lateral projection 38 of theprongs 22 be oriented in a direction substantially perpendicular to thedirection of travel of the disposable diaper on the manufacturing line.A diaper manufacturing line requires complex and expensive machinery tocut, reorient and apply the fastening system 20 if the maximum lateralprojection 38 of the prongs 22 are oriented in the machine direction. Afastening system 20 of the present invention produced with the maximumlateral projection 38 of the prongs 22 oriented in the cross-machinedirection, however, would not require re-orientation before beingapplied to a disposable diaper. It is therefore very advantageous to beable to manufacture the fastening system 20 of the present inventionwith the maximum lateral projection 38 of the prongs 22 oriented in adirection other than the machine direction.

There are two angles which are made by the shank 28 of prongs 22produced by this process. The shank 28 makes an angle α with the planeof the substrate 24 as discussed hereinbefore, and the shank 28 alsomakes an azimuthal angle (indicated by a letter A, FIG. 7) relative tothe machine direction of the substrate 24. As used herein, the term"azimuthal angle" refers to the angle the maximum lateral projection 38makes relative to the machine direction of the substrate when viewedfrom above. As used herein "viewed from above" refers to viewing theprongs 22 from a direction which is perpendicular to the plane of thesubstrate 24. The term "machine direction" refers to the directiongenerally parallel to the principle direction of transport of thesubstrate 24 as it passes through the nip 70, and is indicated by anarrow 75 in FIG. 7. The azimuthal angle is measured by first determiningthe maximum lateral projection 38 of the prong 22 as disclosedhereinbefore. As shown in FIG. 7 the azimuthal angle, indicted by theletter A, is the angle relative to the machine direction which is madeby a line 60 drawn parallel to the maximum lateral projection 38 whenviewed from above. The azimuthal angle A can be measured relative to themachine direction in either the clockwise or counter-clockwisedirection, but the azimuthal angle will not be greater than 180°. Afastening system 20 suitable for use on a disposable diaper, willpreferably have prongs 22 with an azimuthal angle such that the maximumlateral projection 38 will be oriented in a direction having a vectorcomponent perpendicular to the machine direction of the substrate 24.Thus the prongs 22 may have an azimuthal angle greater than 0 degrees,between about 1 degrees and about 180 degrees, generally the azimuthalangle will be greater than about 20 degrees (20°-180°), greater thanabout 45 degrees (45°-180°), or greater than 60 degrees (60°-180°). Theazimuthal angle of the prongs 22 made using the process described hereinwill preferably be from about 20 degrees to about 160 degrees, morepreferably from about 45 degrees to about 135 degrees and mostpreferably from about 60 degrees to about 120 degrees. In a preferredembodiment shown in FIG. 7, the azimuthal angle of the prongs 22 will beabout 90 degrees.

A method for imparting an azimuthal angle to the fastening system 20 isto bias the prongs 22 of the fastening system 20 while the prongs 22 arepartially or wholly in a liquid state. As used herein the term "bias"refers to providing a force or influencing means in a direction having avector component perpendicular to the machine direction of the substrate24. The prongs 22 may be biased when they are newly formed and have notyet cooled and solidified and are still maleable, or the prongs 22 maybe biased after they have cooled and solidified by reheating the prongs22 so that they are maleable and will turn when biased. There are anumber of methods available to bias the prongs 22 so as to impart anazimuthal angle.

A suitable method for imparting an azimuthal angle, is to bias theprongs 22 by causing gravitational forces to act upon the prongs 22while the prongs 22 are partially or wholly in a liquid state such thatthe gravitational forces will pull the prongs 22 to the desiredazimuthal angle. This can be accomplished by tilting the substrate 24 sothat the plane of the substrate 24 when viewed in the machine direction,would not cut perpendicularly through a plum line, but rather would forman angle other than 90 degrees with a plum line. As the prongs 22 areprinted and severed, the angle, indicated by the letter H in FIG. 8, ofthe substrate 24 relative to the horizontal allows gravitational forcesto act upon the distal ends of the shanks 28 and engaging means 30 andpull the prongs 22 toward the longitudinal side of the substrate 24having the lower altitude. Preferably, the print roll 72 and the backingroll 74 together are tilted or raised on one end from the horizontal, asshown in FIG. 8, so that as the substrate 24 passes through the nip 70of the rolls the longitudinal edges of the substrate 24 will be atnonequal altitudes, and the gravitational forces, indicated by theletter G in FIG. 8, will act upon the prongs 22 to give the shank 28 anangle α with the substrate 24 and an azimuthal angle A (neither angle αor angle A are shown in FIG. 8). The substrate 24 should be tilted sothat the plane of the substrate 24 forms an angle relative to thehorizontal of at least about 15 degrees. Preferably the plane of thesubstrate 24 will be at an angle of at least 30 degrees.

In a nonlimiting example of the process, one may use Bostik polyesterhot melt adhesive #7199 heated to a temperature of about 387° F. (197°C.); a print roll 72, having cells 76 with a diameter of 0.040 inches(0.102 centimeters) and a depth of 0.018 inches (0.046 centimeters),heated to a temperature of about 350° F. (177° C.); a substrate of whitekraft paper having a basis weight of 0.08 milligrams per square metertraveling at a speed of 14 feet (4.266 meters) per minutes; and theprint roll 72 and a backing roll 74 will be inclined to an angle ofabout 30° relative to the horizontal.

Another suitable method for imparting an azimuthal angle is to bias theprongs 22 by applying a pressure differential across the plane of thesubstrate 24 while the prongs 22 are partially or wholly in a liquidstate such that the prongs are forced or drawn to the desired azimuthalangle. This may be accomplished by flowing a liquid or gas across theplane of the substrate 24 in a direction having a vector componentperpendicular to the machine direction. The pressure differential willcause the prongs 22 to turn or reorient toward the side of the substratehaving the lower pressure. Preferably, the pressure differential acrossthe substrate 24 is achieved by creating a high pressure from one sideof the substrate 24 using air jets, air needles or other means wellknown in the art. However, the pressure differential across thesubstrate 24 may also be achieved by producing a low pressure (i.e.,vacuum or partial vacuum) from one side of the substrate 24, or bycreating a high pressure from one side of the substrate 24 and at thesame time creating a low pressure from the other side of the substrate24. The side of the substrate 24 which represents the high pressure orlow pressure side and the angle relative to the machine direction atwhich the fluid flows is dependent upon the azimuthal angle desired. Thefluid medium used will preferably be air, though other gases and liquidsmay also be used. As used herein the term "high pressure" refers to apressure greater than the ambient pressure of the air or other fluidwhich surrounds the prongs 22 as they are being azimuthally angled. Asused herein the term "low pressure" refers to a pressure less than theambient pressure of the air or other fluid which surrounds the prongs 22as they are being azimuthally angled.

It should be understood that it would also be suitable to have the highpressure and/or low pressure originating from other than the sides ofthe substrate 24. That is, the high pressure source and/or low pressuresource may be positioned such that the prongs 22 are forced and/or drawnin more than one direction, giving the fastening system 20 a moreisotropic peel strength. As a nonlimiting example, a vacuum source maybe disposed near the sides of the substrate 24 and a pressure sourcedisposed near the middle of the substrate 24, such that the maximumlateral projection 38 of the prongs 22 will be influenced substantiallyaway from the middle of the substrate 24 and toward the sides of thesubstrate 24.

When a pressure differential is used to impart an azimuthal angle to theprongs 22, frequently turbulence in the chosen fluid medium will causesome of the prongs 22 to scatter, or acquire an undesired azimuthalangle. To minimize the incidence of prongs 22 scattering, it isdesirable to minimize the turbulent flow of the fluid medium andmaintain a more streamline or laminar flow. There are a number ofmethods available to produce a substantially laminar flow.

One method of producing a substantially laminar flow is through the useof one or more nozzles or flow amplifiers to impart controlled directionto a flow. As a non-limiting example, two commercial air flow amplifiers902 will be used in tandem. The first air flow amplifier 902 (indicatedby the letter P in FIG. 9) has the discharge flow of its outlet directedacross the substrate 24. The second air flow amplifier 902 (indicated bythe letter V in FIG. 9) has the suction of its inlet drawing from acrossthe substrate 24. The discharge flow of the first air flow amplifier Pis drawn into the inlet of the second air flow amplifier V creating asubstantially linear air draft. The air flow amplifiers 902 are orientedrelative to the substrate 24 to produce a low velocity linear air draftin a cross-machine direction. The preferred location of the linear airdraft is immediately down stream of the cutting hot wire 78 (not shownin FIG. 9). Extraneous air current may be eliminated by the use of anenclosure (not shown) to surround the area where the linear air draft isapplied. Suitable air flow amplifiers are commercially available fromVortec Corporation of Cincinnati, Ohio and marketed as Transvector Model912/952, having a 25-100 SCFM rating. The required air pressure mayvary, but about 1 psi to about 10 psi of air pressure works well.

Another suitable method for imparting an azimuthal angle to the prongs22 is to bias the prongs 22 by mechanically turning or physicallydragging the prongs 22 while they are partially or wholly in a liquidstate. A non-limiting example of this is the use of an oscillating orrotating severing means, e.g. hot wire, (not shown) to force or drag theprongs 22 to the desired azimuthal angle as the prongs 22 are cut. Therewill be many other methods of accomplishing this which will be apparentto one skilled in the art.

It should also be understood that an azimuthal angle may be imparted tothe prongs 22 by using a combination of methods to bias the prongs 22. Anonlimiting example of the use of combinations of methods is the use ofgravitational force and a pressure differential across the plane of thesubstrate 24 in combination to impart an azimuthal angle to the prongs22. Another non-limiting example is the use of gravitational forces anda rotating severing means in combination to impart an azimuthal angle tothe prongs 22. Many other methods of imparting an azimuthal angle to theprongs 22 will be apparent to one skilled in the art, as will thevarious combinations of methods.

ILLUSTRATIVE ARTICLE OF USE

An illustrative and nonlimiting example of the usage of the fasteningsystem 120 of the present invention in an article of manufacture followsand is illustrated in FIG. 6. Mechanical fastening systems have beenadvantageously used in disposable absorbent articles as disclosed inU.S. patent application Ser. No. 07/132,281, Issue Batch No. N97, filedon Dec. 18, 1987, in the name of Scripps, which application isincorporated herein by reference for the purpose of showing a diaper 110structure and the advantageous utilization of mechanical fasteningsystems 20 in such diaper 120 structures.

It is known, for example, that mechanical fastening systems 120 are lesseasily contaminated by oils and powders than are adhesive tape fasteningsystems and, further, may be easily reused. All of these featuresprovide advantages when applied to a disposable diaper 110 intended foruse on an infant. Also, a refastenable fastening system provides theadvantage that the infant may be checked to see if soiling of thedisposable diaper 110 has occurred during the wearing period.

Referring to FIG. 6, there is shown a disposable diaper 110 intended tobe worn about the lower torso by an infant. As used herein, the term"disposable absorbent article" refers to a garment generally worn byinfants or incontinent persons and which is drawn between the legs,fastened about the waist of the wearer and intended to be discardedafter a single use and not to be laundered or restored. A "disposablediaper" is a particular disposable article intended and scaled to beworn by an infant.

A preferred diaper 110 comprises a liquid pervious topsheet 112, aliquid impervious backsheet 116, and an absorbent core 118 intermediatethe topsheet 112 and backsheet 116. The topsheet 112 and backsheet 116are at least partially peripherally joined to ensure the core 118 isheld in position. The diaper 110 elements may be assembled in a varietyof configurations well known to one skilled in the art, with a preferredconfiguration being generally described in U.S. Pat. No. 3,860,003issued Jan. 14, 1975 to Buell, which patent is incorporated herein byreference for the purpose of disclosing a particularly preferred diaper110 configuration.

The topsheet 112 and backsheet 116 of the diaper 110 are generallycoextensive and at least partially peripherally joined together as notedabove. Joining of the topsheet 112 and backsheet 116 may be accomplishedby a hot-melt adhesive, such as Eastobond A3 manufactured by the EastmanChemical Products Company of Kingsport, Tenn. The absorbent core 118 haslength and width dimensions generally less than that of the topsheet 112and backsheet 116. The core 118 is interposed between the topsheet 112and backsheet 116 in fixed relationship.

The diaper 110 periphery comprises oppositely disposed first and secondends 122 and 124. The diaper 110 has a first waist portion 142 and asecond waist portion 144 extending respectively from the first end 122and second end 124 of the diaper 110 periphery towards the lateralcenterline of the diaper 110 a distance of about one-fifth to aboutone-third the length of the diaper 110. The waist portions 142 and 144comprise those portions of the diaper 110 which, when worn, encircle thewaist of the wearer and are generally at the highest elevation of thediaper 110 when the wearer is in the standing position. The crotch 146of the diaper 110 is that portion of the diaper 110 disposed between thefirst and second waist portions 142 and 144 and which, when worn ispositioned between the legs of the wearer.

The absorbent "core" is any means for absorbing and retaining liquidbody exudates. The absorbent core 118 is generally compressible,conformable, and nonirritating to the skin of the wearer. A preferredcore 118 has first and second opposed faces and may, if desired, befurther encased by tissue layers. One opposed face of the core 118 isoriented towards the topsheet 112 and the other opposed face is orientedtowards the backsheet 116.

The absorbent core 118 is superimposed on the backsheet 116 andpreferably joined thereto by any means well known in the art such asadhesive bonding. In a particularly preferred embodiment, adhesivebonding is accomplished by longitudinal adhesive bands which join thecore 118 to the backsheet 116. The backsheet 116 is impervious toliquids and prevents liquids absorbed by and contained in the absorbentcore 118 from wetting undergarments, clothing, bedding and any otherobjects which contact the diaper 110. As used herein, the term"backsheet" refers to any barrier disposed outwardly of the core 118 asthe diaper 110 is worn and which contains absorbed liquids within thediaper 110. Preferably, the backsheet 116 is a polyolefinic film ofabout 0.012 to about 0.051 mm (0.0005-0.002 inches) in thickness. Apolyethylene film is particularly preferred, with a suitable film beingmanufactured by the Monsanto Company of St. Louis, Mo. as film No. 8020.If desired, the backsheet 116 may be embossed or matte finished toprovide a more clothlike appearance or be provided with passages topermit escape of vapors.

The topsheet 112 is compliant, tactily pleasing and nonirritating to thewearer's skin. The topsheet 112 prevents contact of the absorbent core118 and liquids therein with the skin of the wearer. The topsheet 112 isliquid pervious, permitting liquids to readily penetrate therethrough.As used herein, the term "topsheet" refers to any liquid pervious facingwhich contacts the skin of the wearer while the diaper 110 is being wornand prevents the core 118 from contacting the skin of the wearer. Thetopsheet 112 may be made of woven, nonwoven, spunbonded or cardedmaterials. A preferred topsheet 112 is carded and thermally bonded bymeans to those skilled in the nonwoven fabrics art. A particularlypreferred topsheet 112 has a weight of about 18 to about 25 grams persquare meter, a minimum dry tensile strength of about 400 grams percentimeter in the machine direction and a wet tensile strength of atleast about 55 grams per centimeter in the cross-machine direction.

The diaper 110 is provided with a fastening system 120 and receivingsurface 153 for maintaining the first waist portion 142 and second waistportion 144 in an overlapping configuration when the diaper 110 is worn,so that the diaper 110 is secured to the wearer. Thus, the diaper 110 isfitted to the wearer and a side closure is formed when the fasteningsystem 120 is secured to the receiving surface 153.

The fastening system 120 should resist the separation forces which occurduring the wearing period. The term "separation forces" refers to forcesacting on the fastening system 120 and receiving surface 153 which tendto cause separation, release or removal of the fastening system 120 fromthe receiving surface 153. Separation forces include both shear and peelforces. The term "shear force" refers to distributive forces actinggenerally tangential to the receiving surface 153 and which may bethought of as being generally parallel to the plane of the substrate ofthe fastening system 120. The term "peel forces" refers to distributiveforces acting in the generally longitudinal direction, and perpendicularto the plane of the receiving surface 153 and fastening system 120substrates.

Shear forces are measured by tensile pulling of the fastening system 120and receiving surface 153 in opposite directions generally parallel tothe planes of the respective substrates. The method used to determinethe resistance of a fastening system 120 and receiving surface 153 toshear forces is more fully set forth in U.S. Pat. No. 4,699,622 issuedOct. 13, 1987, to Toussant et al., which patent is incorporated hereinby reference for the purpose of describing the measurement of shearforces.

Peel forces are measured by tensile pulling of the fastening system 120from the receiving surface 153 at an included angle of about 135°. Themethod used to determine the resistance of a fastening system 120 andreceiving surface 153 to peel forces is more fully set forth in U.S.patent application Ser. No. 07/132,281, Issue Batch No. N87, filed Nov.18, 1987 in the name of Scripps, which application is incorporatedherein by reference for the purpose of describing the measurement ofpeel forces.

Separation forces are typically generated by movements of the wearer orby the wearer trying to unfasten the diaper 110. Generally, an infantshould not be able to unfasten or remove a diaper 110 the infant iswearing, nor should the diaper 110 come unfastened in the presence ofordinary separation forces which occur during normal wearing. However,an adult should be able to remove the diaper 110 to change it whensoiled or check to see if soiling has occurred. Generally, the fasteningsystem 120 and receiving surface 153 should resist a peel force of atleast 200 grams, preferably at least about 500 grams, and morepreferably, at least about 700 grams. Furthermore, the fastening system120 and receiving surface 153 should resist a shear force of at least500 grams, preferably at least about 750 grams, and more preferably atleast about 1,000 grams.

The receiving surface 153 may be disposed in a first position anywhereon the diaper 110, so long as the receiving surface 153 engages thefastening means to maintain the first and second waist portions 144 inan overlapping configuration. For example, the receiving surface 153 maybe disposed on the outside surface of the second waist portion 144, onthe inside surface of the first waist portion 142, or any other positionon the diaper 110 on which it is disposed so as to engage with thefastening system 120. The receiving surface 153 may be integral, adiscrete element joined to the diaper 110, or a single piece of materialthat is neither divided or discontinuous with an element of the diaper110, such as the topsheet 112 or backsheet 116.

While the receiving surface 153 may assume various sizes and shapes, thereceiving surface 153 preferably comprises one or more integral patchespositioned across the outside surface of the second waist portion 144 toallow for maximum fit adjustment at the waist of the wearer. Asillustrated in FIG. 6, the receiving surface 153 is preferably anelongate rectangularly shaped integral member secured to the outersurface of the second waist portion 144.

A suitable receiving surface 153 is a nonwoven fabric, is stitchbondedor any other type of fiber or loop material well known in the art. Thereceiving surface 153 may be manufactured from a variety of materialswhich provide fiber elements, and preferably loops capable of beingintercepted and retained by the engaging means. Suitable materialsinclude nylon, polyester, polypropylene and combinations of theforegoing. A suitable receiving surface 153 comprises a number of fiberloops projecting from a woven and is commercially available asScotchmate brand nylon woven loop No. FJ3401, sold by the MinnesotaMining and Manufacturing Company of St. Paul, Minn. Another suitablereceiving surface 153 comprises a tricot having a plurality of nylonfilament loops projecting from a nylon backing and is commerciallyavailable from Gilford Mills of Greensboro, N.C. and designated GilfordNo. 16110. A particularly preferred receiving surface is stitchbondedloop material sold by the Milliken Company of Spartanburg, S.C. underNumber 970026.

The fastening system 120 is intended to engage the complementaryreceiving surface 153 to provide a secure fit for the diaper 110. Thefastening system 120 may comprise any of the well known configurationsutilized for achieving a side closure on a disposable diaper 110. Thefastening system 120 substrate is joined to the diaper 110 in spacedrelationship from the receiving means 153. As shown on FIG. 6, thefastening system 120 is preferably disposed on both the first and secondlongitudinal sides of the diaper 110. A preferred configuration for thefastening system 120 minimizes any potential contact between the prongsof the fastening system 120 and the skin of the wearer. A preferredfastening system 120 disposition is a Y-shaped tape arrangement,described in detail in U.S. Pat. No. 3,848,594 issued Nov. 19, 1974 toBuell. An alternatively preferred fastening system 120 arrangement isdescribed in detail in U.S. Pat. No. 4,699,622 issued Oct. 13, 1987 toToussant et al., both of which patents are incorporated herein byreference for the purpose of illustrating various placements of thefastening system 120 on the disposable diaper 110.

The fastening system 120 of FIG. 6 has a manufacturer's end 156 and anoppositely disposed user's end 158. The manufacturer's end 156 is joinedto the diaper 110, preferably in juxtaposition with the first waistportion 142. The user's end 158 is the free end and is secured to thereceiving surface 153 when the diaper 110 is secured to the wearer.

After the diaper 110 is fitted about the waist of the wearer, the user'send 158 of the fastening system 120 is releasably secured to thereceiving surface 153, and preferably positioned on the second waistportion 144, thereby causing the diaper 110 to encircle the waist of thewearer. The diaper 110 has now effected a side closure. The prongs (notshown) extend from the fastening system 120 of the user's end 158 sothat the prong engaging means intercept the strands of the receivingsurface 153.

A fastening system 120 and complementary receiving surface 153 whichprovides a resistance to peel forces in excess of 700 grams and aresistance to shear forces in excess of 1,000 grams may be constructedas follows according to the specific parameters of the fastening system120 set forth in the aforementioned "Process of Manufacture." Thecomplementary receiving surface 153 used in conjunction with thefastening system 120 is the aforementioned Milliken Company No. 970026stitchbonded loop fabric.

The fastening system 120 is at least about 2.54 centimeters (1 inch) inwidth and may be of any length which provides a convenient user's end158, with a length of at least about 3.5 centimeters (1.4 inches) beingpreferred. The array of the prongs of fastening system 120 comprises amatrix having about 26 prongs per square centimeter (169 prongs persquare inch). The prongs are preferentially oriented in substantiallythe same direction and face the user's end 158 of the fastening tape.

In use, the diaper 110 is applied to the wearer by positioning the firstwaist portion 142 around the wearer's back and drawing the remainder ofthe diaper 110 between the legs of the wearer so that the second waistportion 144 is disposed across the front of the wearer. The user's ends158 of the fastening system 120 are then secured to the receivingsurface 153 on the outside surface of the second waist portion 144 toform a side closure.

What is claimed is:
 1. An article having a machine direction and across-machine direction comprising:a substrate; and a fastening systemfor attaching to a complimentary receiving surface, said fasteningsystem comprising a multiplicity of prongs, each said prong comprising:ashank joined to said substrate at a base, said shank having a proximalend contiguous with said base and projecting outwardly from saidsubstrate, said shank being nonperpendicularly oriented relative to theplane of said substrate, said shank further having an azimuthal anglebetween about 20° and about 160°; and an engaging means joined to saidshank and projecting laterally beyond the periphery of said shank. 2.The article of claim 1 wherein said shank has an azimuthal angle rangingfrom about 45° to about 135°.
 3. The article of claim 1 wherein saidshank has an azimuthal angle ranging from about 60° to about 120°. 4.The article of claim 1 wherein said shank has an azimuthal angle ofabout 90°.
 5. The article of claim 1 wherein each said prongadditionally comprises a shank having a leading angle and a trailingangle, said leading angle being substantially different from saidtrailing angle.
 6. An absorbent article comprising:a topsheet; abacksheet joined with said topsheet; an absorbent core positionedbetween said topsheet and said backsheet; and a fastening systemcomprising:a substrate; and a multiplicity of prongs, each said prongcomprising:a shank joined to said substrate at a base, said shank havinga proximal end contiguous with said base and projecting outwardly fromsaid substrate, said shank being nonperpendicularly oriented relative tothe plane of said substrate, said shank further having an azimuthalangle between about 20° and about 160°; and an engaging means joined tosaid shank and projecting laterally beyond the periphery of said shank.7. The absorbent article of claim 6, further comprising a complementaryloop fastening material comprising at least one fibrous element, saidloop fastening material being joined to said outer cover such that atleast one of said prongs of said fastening system is capable ofmechanically entangling said fibrous element.
 8. The absorbent articleof claim 6, further comprising a tape having a first end and a secondend, said first end being joined to said outer cover and said fasteningsystem being joined to said second end.
 9. The absorbent article ofclaim 8, further comprising a complementary loop fastening materialcomprising at least one fibrous element, said loop fastening materialbeing joined to said outer cover such that at least one of said prongsof said fastening system is capable of mechanically entangling saidfibrous element.
 10. An absorbent article comprising:an outer covercomprising a liquid pervious topsheet and a liquid impervious backsheetjoined to said topsheet; an absorbent core positioned between saidtopsheet and said backsheet; and a fastening system joined to said outercover, said fastening system comprising:a substrate; and a multiplicityof prongs, each said prong comprising:a shank joined to said substrateat a base, said shank having a proximal end contiguous with said baseand projecting outwardly from said substrate, said shank having aleading angle and a trailing angle, said leading angle beingsubstantially different from said trailing angle, said shank beingnonperpendicularly oriented relative to the plane of said substrate,said shank further having an azimuthal angle between about 20° and about160°; and an engaging means joined to said shank and projectinglaterally beyond the periphery of said shank.
 11. The absorbent articleof claim 10 wherein said shank has an azimuthal angle ranging from about45° to about 135°.
 12. The absorbent article of claim 10 wherein saidshank has an azimuthal angle ranging from about 60° to about 120°. 13.The absorbent article of claim 10 wherein said shank has an azimuthalangle of about 90°.
 14. The absorbent article of claim 10 wherein saidsubstrate of said fastening system comprises at least a portion of saidouter cover.
 15. The absorbent article of claim 10 additionallycomprising a pair of tapes, each of said tapes comprising a first endand a second end, said first end being joined to said outer cover andsaid second end having said fastening system joined thereto.
 16. Theabsorbent article of claim 15 wherein said shank has an azimuthal angleranging from about 45° to about 135°.
 17. The absorbent article of claim15 wherein said shank has an azimuthal angle ranging from about 60° toabout 120°.
 18. The absorbent article of claim 15 wherein said shank hasan azimuthal angle of about 90°.
 19. The absorbent article of claim 15wherein at least a portion of said second end of each of said tapesforms said substrate of said fastening system.